1. Field of the Invention
The present invention pertains to an ophthalmic surgical device, and more importantly, pertains to a specific adaptation of the gonio puncture surgical technique, utilizing a hollow needle rather than a knife.
2. Description of the Prior Art
Glaucoma is one of the chief causes of blindness in adults in the United States and Europe. It is a condition in which intraocular pressure becomes too high and destroys ganglion cells of the retina and the nerve fibers of the optic nerve producing blindness. When the intraocular pressure cannot be controlled with medications, surgery is necessary.
In the normal eye, fluid is pumped in by the epithelial cells lining the surface of the ciliary body. This fluid passes forward through the pupil and into the anterior chamber of the eye. It is drained through a sieve-like filter called the trabecular meshwork, into the drainage Channel of Schlemm and out into the aqueous veins. In patients with glaucoma this drainage mechanism fails causing build up of excess pressure. The purpose of surgery is to create a new drainage system to maintain a lower ambient pressure.
The commonly employed operation today is a fistulizing procedure called trabeculectomy. In this operation the conjunctiva is lifted away from the sclera, and a flap of sclera is lifted extending far enough forward to expose the normal filtering area (the limbus), an opening is made through this limbal area into the anterior chamber, removing a section of tissue to create a permanent defect, and the scleral flap is replaced (as a guard) and the conjunctiva closed.
The operation has technical problems, and a number of well recognized hazards. In addition, it fails immediately in at least 15% of patients, and long term in a much higher percentage. Because a large area of the limbus has been disturbed (about 25%) and because of the damage to the eye that may be produced by the postoperative inflammation that such extensive surgery causes and other possible complications, re-operation is difficult and the number of re-operations possible is limited.
A much simpler procedure has been practiced from time to time, going back as far at least as Von Graefe in the 1850s, used extensively by Barkan in the 1930s and 40s, and still employed in some third world countries where speed, simplicity, and lack of complications outweigh the high failure rate. This procedure is called gonio puncture. In this operation a thin knife is simply introduced across the anterior chamber and a puncture made from inside the eye outward into the space beneath the conjunctiva. The knife is then withdrawn and fluid allowed to drain through this puncture wound. There are no flaps, no sutures, very few complications, and almost no postoperative reaction. Unfortunately, there is a high failure rate, simply because the puncture wound heals.
There is a long history of the use of setons to try to improve the success rate of ordinary filtering surgery. Materials have included the patient's own iris and a variety of metals and plastics. The latter have been fashioned to act as wicks, stints, or tubes. The procedure for placing these devices is a modification of a standard filtering operation. Unfortunately, the same postoperative inflammatory and healing response which causes filtering surgery to fail also seals off the seton, so that most of these devices have had a high rate of failure and very little popularity. There are a few current seton approaches which have a higher rate of success, but these involve very extensive surgery, very large devices, and are used only in desperate cases.
The present invention combines the simplicity and safety of gonio puncture with the advantages of a seton to keep the puncture wound open. It can be repeated, if needed, much more readily because of the minimal disturbance of the eye produced by this approach.